US8953650B2 - Method to control emission wavelength of tunable laser diode - Google Patents
Method to control emission wavelength of tunable laser diode Download PDFInfo
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- US8953650B2 US8953650B2 US13/653,958 US201213653958A US8953650B2 US 8953650 B2 US8953650 B2 US 8953650B2 US 201213653958 A US201213653958 A US 201213653958A US 8953650 B2 US8953650 B2 US 8953650B2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0607—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature
- H01S5/0612—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature controlled by temperature
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06255—Controlling the frequency of the radiation
- H01S5/06256—Controlling the frequency of the radiation with DBR-structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
- H01S5/0687—Stabilising the frequency of the laser
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/024—Arrangements for thermal management
- H01S5/02407—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling
- H01S5/02415—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling by using a thermo-electric cooler [TEC], e.g. Peltier element
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
- H01S5/0265—Intensity modulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06255—Controlling the frequency of the radiation
- H01S5/06258—Controlling the frequency of the radiation with DFB-structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/1206—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers having a non constant or multiplicity of periods
- H01S5/1212—Chirped grating
Definitions
- the present application relates to a method to control a tunable laser diode (hereafter denoted as LD).
- thermo-electric cooler hereafter denoted as TEC
- TEC thermo-electric cooler
- the apparatus performs a sequence to sense a temperature of the tunable LD, and to feedback this sensed temperature to the TEC to adjust the temperature of the tunable LD.
- WDM wavelength division multiplexing
- a tunable LD whose emission wavelength is precisely adjustable to a target wavelength, which is one of the grid wavelengths of the WDM system, has been attracted.
- Conventional tunable LDs generally configure with a gain region having a gain spectrum with a plurality of peaks and a wavelength selective region generally having a reflection spectrum with a plurality of reflection peaks.
- Such a tunable LD may emit light with an emission wavelength at which one of gain peaks attributed to the gain region coincides with one of reflection peaks attributed to the wavelength selective region.
- the tunable LD may emit light with the target wavelength.
- Such a tuning of the emission wavelength generally requires a time until the emission wavelength becomes stable at the target wavelength.
- One standard set in the optical source for the WDM system requires the switching of the target wavelength, that is, from receiving the command to switch the target wavelength to stabilizing the wavelength at the target one to be several tenses of milli-seconds at most.
- the TEC generally dominates the switching of the emission wavelength, which sometimes requires several seconds.
- An aspect of the present application relates to a method to control an emission wavelength of a tunable LD, which may configure with a sampled grating distributed feedback (SG-DFB) region as the first region and a chirped sampled grating distributed Bragg reflector (CSG-DBR) region as the second region.
- the first regions may be stimulated with a current as the first stimulus to tune the emission wavelength, while, the second region may be stimulated with heat as the second stimulus to tune the emission wavelength.
- a feature of the method is that: (a) calculates a first derivative of the emission wavelength against the first stimulus and a second derivative of the emission wavelength against the second stimulus; (b) adjusting the first stimulus by a first deviation to coincide the emission wavelength with a target wavelength; (c) adjusting a target stimulus for the second stimulus based on the first deviation of the first stimulus, the first derivative and the second derivative; (d) adjusting the second stimulus by a second deviation to coincide with the second stimulus with the target stimulus.
- FIG. 1 schematically shows a functional block diagram of an apparatus for controlling a tunable LD according to an embodiment of the invention
- FIG. 2A shows a relation of an emission wavelength of the tunable LD against the tuning current and the heater temperature
- FIG. 2B magnifies one band of the relation where the emission wavelength is determined by one of the gain peaks determined by the tuning current and one of the reflection peaks determined by the heater temperature;
- FIG. 3 schematically illustrates a functional arrangement of the controller appeared in FIG. 1 ;
- FIG. 4A is a flow chart of the control sequence of the emission wavelength of the tunable LD, and FIG. 4B is another flow chart of the control sequence;
- FIGS. 5A and 5B are flow charts of the control sequence of the emission wavelength of the tunable LD according to modified embodiments of the invention.
- FIG. 6 schematically shows a function block diagram of another apparatus according to another embodiment of the invention.
- FIG. 1 schematically illustrates functional blocks of a tunable LD and an apparatus 1 including the tunable LD 10 to operate the tunable LD 10 according to an embodiment of the invention.
- the apparatus 1 includes a thermo-electric cooler (TEC) 12 , typically a Peltier device, to control a temperature of the tunable LD 10 placed thereon, a temperature sensor 14 , typically a thermistor, to sense a temperature of the tunable LD 10 , a wavelength monitor 16 to monitor an emission wavelength of the tunable LD 10 , and a controller 18 to control the emission wavelength and the optical output power of the tunable LD 10 .
- TEC thermo-electric cooler
- FIG. 1 places the wavelength monitor 16 in the front of the tunable LD 10
- the apparatus 1 may place the wavelength monitor 10 in the rear of the tunable LD 10 to detect a back facet light.
- the wavelength monitor 16 includes two photo detectors, one of which detects light coming directly from the tunable LD 10 without intervening any optical device whose optical characteristics depend on wavelengths; while, the other detect the light by intervening an optical device with a wavelength dependent characteristics, typically an etalon filter.
- the apparatus 1 may detect a shift of the emission wavelength of the tunable LD 10 because an etalon filter has a periodic transmittance and the other photo detector varies an output thereof corresponding to the transmittance of the optical device.
- the outputs of two photo detectors are provided to the controller 18 .
- the tunable LD 10 whose emission wavelength is a subject to be controlled, will be described in an arrangement thereof.
- the tunable LD 10 of the embodiment includes a chirped sampled grating distributed Bragg reflector (hereafter denoted as CSG-DBR) region 22 as a second region, a sampled grating distributed feedback (hereafter denoted as SG-DFB) regions 24 as a first region, and a semiconductor optical amplifier (hereafter denoted as SOA) region 26 , where these regions, 22 to 26 , are arranged along the optical axis thereof in this order.
- CSG-DBR sampled grating distributed Bragg reflector
- SG-DFB sampled grating distributed feedback
- SOA semiconductor optical amplifier
- the CSG-DBR region 22 includes an optical waveguide providing a plurality of grating regions each having an optical grating and being apart by spaces, by which the CSG-DBR region 22 shows a reflectance spectrum with a plurality of reflection peaks.
- the span between the reflection peaks attributed to the CSG-DBR region 22 is slightly different from a space between the gain peaks attributed to the SG-DFB regions 24 , which will be described in detail later.
- the tunable LD 10 may emit light with the wavelength at which one of reflection peaks of the CSG-DBR region 22 coincides with one of gain peaks of the SG-DFB region 24 .
- the CSG-DBR region 22 provides a heater 28 monolithically integrated thereon.
- the controller 18 by supplying electrical power to the heater 28 as a second stimulus for the CSG-DBR region 24 , modifies refractive index of the optical waveguide in the CSG-DBR region 22 , which shifts the wavelengths of the reflection peaks and one of the peak wavelengths becomes coincides with the wavelength of the gain peaks attributed to the SG-DFB region 24 .
- the reflection peaks and the gain peaks shift the wavelengths thereof dependent on an operating temperature of the tunable LD 10 .
- the SG-DFB region 24 will be described.
- the SG-DFB region 24 also includes an optical waveguide provided with a plurality of gain regions and a plurality of tuning regions. Each of the gain regions provides an optical grating; while, the tuning regions provide no optical grating. These gain regions and the tuning regions are alternately arranged along the optical axis of the tunable LD 10 .
- the SG-DFB region 24 thus configured shows a gain spectrum with a plurality of gain peaks with a predetermined span.
- the SG-DFB region 24 further provides two type of electrodes, 32 and 33 , the former of which injects a driving current into the gain region, while, the latter injects another current, namely a tuning current, into the tuning region.
- the refractive index of the tuning region may be modified by the injected current as a first stimulus, then the peak wavelength may be shifted and the span therebetween may be faintly modified.
- the wavelengths of the gain peaks, and the span therebetween may be also varied depending on the operating temperature of the tunable LD 10 .
- the SOA 26 also includes an optical waveguide and an electrode 34 to control the amplification factor of the waveguide in the SOA 26 . Injecting carriers from the electrode 34 , the amplification factor of the optical waveguide in the SOA 26 may be controlled.
- the optical waveguide in the CSG-DBR region 22 , that in the SG-DFB region 24 , and that in the SOA 26 are optically coupled to each other.
- the tunable LD 10 of the embodiment thus configured may tune the emission wavelength thereof by controlling the electrical power supplied to the heater 28 in the CSG-DBR region 22 as the second stimulus and the injection current injected into the tuning region as the first stimulus.
- FIGS. 2A and 2B show behaviors of the emission wavelength Wp of the tunable LD 10 depending on the injection current into the tuning region in the horizontal axis, and the heater temperature in the vertical axis, as the operating temperature of the tunable LD 10 is kept constant.
- Solid lines in FIG. 2A denote thresholds at which the emission wavelength hops. That is, in a band region surrounded by two solid curves, which extends from the top left to the bottom right, a combination of the reflection peak and the gain peak is maintained, while, at least one of the reflection peak and the gain peak hops to another at the solid curves to form a new combination.
- FIG. 2B magnifies a square portion in FIG. 2A .
- the emission wavelength Wp shifts longer from the bottom right to the top left within the band region, namely, from 1547.10 to 1547.16 nm.
- the reflection peak hops to another as the emission wavelength Wp shifts only by 0.01 nm.
- the gain peak hops to another as the emission wavelength Wp shifts only by 0.04 nm.
- the emission wavelength Wp does not shift smoothly and stably.
- the injection current is reduced by a preset amount while the heater temperature is raised relative to the preset amount, the emission wavelength Wp shifts along a solid line in FIG. 2B as the combination of the gain peak and the reflection peak is maintained.
- the present embodiment is to provide an algorithm to control the emission wavelength of the tunable LD 10 by setting variably the injection current and the heater temperature which is equivalently power supplied to the heater.
- the controller 18 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a power supply, a monitoring unit including analog-to-digital converters (A/D-Cs), and so on. These elements in the controller 18 may be separately prepared independent of the controller 18 .
- the RAM and/or ROM holds initial conditions and target conditions as a look-up-table (LUT), where these conditions correspond to the emission wavelength of the tunable LD 10 .
- the outputs of the controller 18 are supplied to respective regions, 22 to 26 , of the tunable LD 10 via electrodes, 30 to 34 .
- the controller 18 first sets the temperature of the tunable LD 10 in the target temperature by controlling the TEC 12 through the temperature sensor 14 . This target temperature is maintained independent of the emission wavelength. Then, the controller 18 supplies biases for respective regions, 22 to 26 , via electrodes, 30 to 34 , where the biases are measured in advance to the practical operation and held in the LUT 20 .
- the emission wavelength is set to be close to the target wavelength, but not always set in just target wavelength within an acceptable range because of a varied ambient temperature, a long-term degradation of the tunable LD 10 , and so on.
- the target wavelength is generally set to be one of the gird wavelengths of the wavelength division multiplexing (WDM) system.
- the controller 18 is necessary to adjust the emission wavelength by the feedback loop so as to coincide the emission wavelength with the target wavelength within a preset range.
- FIG. 3 schematically shows a functional block diagram of the feedback loop.
- the feedback loop includes the first loop L 1 and the second loop L 2 , the former of which includes a divider 40 for calculating a ratio I PD2 /I PD1 of the outputs of two photo detectors, a subtracter 42 to subtract the ratio I PD2 /I PD1 from a value t_lambda corresponding to the target wavelength, an amplifier 44 to amplify the subtracted result (t_lambda ⁇ I PD2 /I PD1 ) by a gain G 1 , and an adder 46 to increase/decrease an amplified result G 1 ⁇ (t_lambda ⁇ I PD2 /I PD1 ) to/from the initial tuning current I tune — ini to generate the tuning current I tune , which is supplied to the tuning region.
- I PD1 and I PD2 are the photocurrents each output from the photo detectors that detect the optical output directly from the tunable LD 10 and the optical output indirectly through the etalon filter.
- the value t_lambda corresponds to the ratio I PD2 /I PD1 when the tunable LD 10 emits light with the target wavelength. Accordingly, the subtracter 42 calculates a difference between the target wavelength and a wavelength of the light which the tunable LD 10 currently emits.
- the photo detectors in the outputs thereof become faint or zero at the starting-up or during the initialization processes; then the ratio I PD2 /I PD1 is indefinite. Accordingly, the subtracter 42 outputs zero by the control signal CTRL 1 .
- the amplifier 44 has a gain G 1 large enough; or the amplifier 44 may be an integrator in an alternative. Because the output of the subtracter 42 is set to be zero as described above, the output of the amplifier 44 is also set to be zero, then the first loop L 1 directly outputs the initial tuning current I tune — ini .
- the system resets the control signal CTRL 1 to operate the subtracter 42 . Then, the first loop L 1 becomes active to set the tuning current I tune supplied to the gain region in a value by which the ratio I PD2 /I PD1 of the outputs of two photo detectors becomes the target value t_lambda.
- the second loop L 2 includes a multiplier 48 , a subtracter 50 , an amplifier 52 , and an adder 54 .
- the multiplier 48 evaluates power currently supplied to the heater 28 by detecting the heater voltage V heater caused by the heater current I heater presently flowing in the heater 28 .
- the subtracter 50 subtracts the power currently supplied to the heater 28 from the target power.
- the amplifier 52 amplifies the output of the subtracter 50 by the gain G 2 .
- the adder 54 increases/decreases an amplified result to/from the initial heater current I heater — ini to evaluate the heater current I heater to be supplied to the heater 28 .
- the amplifier 52 in the second loop L 2 also has a gain G 2 large enough, or in an alternative, the amplifier 52 may be an integrator.
- the control signal CTRL 2 also sets the output of the subtracter 50 to be zero during the initializing of the second loop L 2 , which sets the output of the amplifier 50 to be also zero. Then, the second loop L 2 outputs the initial heater current I heater — ini as the heater current I heater .
- the second loop L 2 starts the operation. That is, the subtracter 50 subtracts the target heater power from the currently supplied power, the amplifier 52 amplifies the difference between the target power and the currently supplied power, and the adder 54 increases/decreases the amplified difference of the heater current by the initial heater current I heater — ini as a reference.
- the present embodiment controls the integrated heater based on the power supplied thereto because the control of only one of the heater current and the heater voltage is unable to compensate the degradation of the monolithically integrated heater.
- the controller 18 first sets, by reading the LUT in the memory, the initial conditions of the amplifying current I SOA — ini , the heater current I heater — ini , and the tuning current I tune — ini in respective regions of the tunable LD 10 to activate practically. At that time, the first loop L 1 for the tuning current I tune and the second loop L 2 for the heater current I heater are cut the feedback control thereof by setting the control signals, CTRL 1 and CTRL 2 , respectively. The controller 18 further reads the target value t_lambda for the ratio I PD2 /I PD1 of the outputs of two photo detectors and that t_P heater for the heater.
- the emission wavelength Wp of the tunable LD is set to be close enough to the target wavelength, and the ratio I PD2 /I PD1 of the outputs of two photo detectors is also set to be close to the target value t_lambda.
- the second loop L 2 provides an amplifier 56 and the adder 58 to determine a target condition of the heater power.
- the gain of this amplifier 56 is set to be, for instance, ⁇ in advance to the practical operation.
- the amplifier 56 multiplies the output of the amplifier 44 , which is the deviation of the ratio I PD2 /I PD1 of the outputs of two photo detectors from the target value t_lambda but amplified by the amplifier 44 , by the gain ⁇ , and adds the output thereof to the target power t_P heater .
- the adder 58 in the second loop L 2 adds this deviation, the deviation of the tuning current ⁇ I tune multiplied by the ratio of two derivatives a/b to the target power t_P heater to adjust the target power t_P heater .
- the second loop L 2 performs the feedback control for the heater based on the adjusted target power t′_P heater that reflects the deviation of the tuning current from the target value.
- the first loop L 1 has a response, which is a time from a supplement of a revised tuning current to a shift of the emission wavelength, longer than a response of the second loop L 2 , which is a time from a supplement of a revised heater current to a shift of the emission wavelength.
- the first loop determines the tuning current I tune by adding a deviation from the target current to the initial tuning current I tune — ini , and the tuning current I tune is supplied to the SG-DFB region 24 that shows a quite fast response from the carrier injection to the change of the refractive index or to the shift of the emission wavelength.
- the second loop first adjusts the target heater power based on the result obtained in the first loop L 1 and the amplifier 56 , then calculates the deviation of the current heater power from this adjusted target power.
- the heater provided in the CSG-DBR region 22 of the present embodiment shows relatively fast response because of a reduced size thereof with a limited thermal capacity to be heated. Accordingly, the response of the second loop L 2 depends on time constants attributed to other elements. Thus, the time constant of the first loop L 1 is set to be longer than that of the second loop L 2 to operate two feedback loops, L 1 and L 2 , stably.
- the SG-DFB region 24 and the CSG-DBR region 22 each is controlled by respective loops, L 1 and L 2 , attributed with the time constants different from others.
- the closed loop gain of the first loop L 1 is smaller than that of the second loop L 2 .
- the gain G 1 of the amplifier 44 in the first loop L 1 substantially determines the response of the SG-DFB region 24
- the gain G 2 of the amplifier 52 affects the response of the second loop L 2 .
- the response of the loops, L 1 and L 2 are easily adjusted by varying the gain of the amplifiers, 44 and 52 . For instance, setting the maximum deviation of the tuning current I tune for respective cycles of the loop small enough, where the deviation is added to the initial tuning current I tune — ini , the response of the first loop L 1 in the time constant thereof becomes longer.
- An alternative may set a period to monitor the emission wavelength longer in the first loop L 1 , and set a process to calculate parameters based on this monitoring longer compared with a process to calculate parameters based on the heater current and the heater voltage in the second loop L 2 .
- Still another alternative may set the period to monitor the emission wavelength in the first loop L 1 substantially equal to a period to monitor the heater voltage in the second loop L 2 , and set a frequency to calculate parameters done after the monitoring in the first loop L 1 less than a frequency to calculate parameters in the second loop L 2 .
- the setting of the loop gain of the first loop L 1 and that of the second loop L 2 may be done together with the setting of the frequency of the calculation in the first and second loops, L 1 and L 2 .
- FIG. 4A is a flow chart that sequentially performs the first loop L 1 to control the tuning current I tune and the second loop L 2 to control the heater current I heater .
- the sequence of FIG. 4A first evaluates the tuning current I tune for the wavelength shift ⁇ by one cycle of the first loop L 1 ; then, this evaluated current is not only provided to the next cycle of the first loop L 1 but used for calculating the target heater power ⁇ I Heater combined with the gain ⁇ .
- the sequence shown in FIG. 4A assumes that the operation is done digitally.
- initial conditions read from the LUT 20 such as the initial tuning current I tune — ini , the initial heater current I heater — ini and so on, are set in the tunable LD 10 at step S 01 .
- two control signals, CTRL 1 and CTRL 2 are asserted to provide the initial conditions above to respective regions in feed-forward under the open loop mode.
- the tunable LD 10 being provided with initial conditions, emits light with a wavelength close to the target wavelength provided from the outside of the control loops, L 1 and L 2 , at step S 02 .
- the controller 18 monitors the output of two photo detectors, I PD1 and I PD2 , and calculates the ratio I PD2 /I PD1 therebetween to determine the current emission wavelength at step S 03 . Then, the controller 18 adjusts or modifies the deviation of the tuning current ⁇ I tune to coincide the emission wavelength with the target wavelength at step S 04 . Subsequently, the controller 18 calculates the target heater power based on the deviation of the tuning current ⁇ I tune and the gain a at step S 05 . The controller 18 performs step S 03 after the revised heater power is set to the heater. Thus, the controller 18 may make the emission wavelength to coincide with the target wavelength by circulating steps from S 03 to S 05 .
- the controller 18 may perform two loops, L 1 and L 2 , concurrently as shown in FIG. 4B .
- the first loop L 1 evaluates the deviation of the tuning current ⁇ I tune and sets the target heater power based on the this deviation of the tuning current ⁇ I tune same as the sequence shown in FIG. 4A , but the first loop L 1 starts the next cycle at step S 14 independent of the setting of the revised heater power at step S 15 because the time constant of the second loop L 2 is shorter than that of the first loop L 1 .
- the controller 18 may make the emission wavelength of the tunable LD 10 to coincide with the target wavelength by iterating steps S 13 to S 15 .
- the method of the embodiment may perform the feedback control for the tuning current concurrently with the feedback control for the heater current, which enables the emission wavelength of the tunable LD to coincide with the target wavelength promptly and stably.
- the time constant of the first feedback loop L 1 for the tuning current is set to be longer than the time constant of the second feedback loop L 2 for the heater power, which enables the response of the emission wavelength against the tuning current to be close to the response against the heater power.
- the target heater power is stably set for the current emission wavelength, which makes the control for the emission wavelength promptly.
- the tunable LD 1 may provide a function to correct the initial heater power.
- Sequences shown in FIGS. 5A and 5B add a sequence to correct the initial heater power to sequences shown in FIGS. 4A and 4B , respectively.
- Steps in FIG. 5A except for steps S 23 , S 24 , S 28 , and S 29 correspond to steps S 01 to S 05 in FIG. 4A
- steps in FIG. 5B except for steps S 43 , S 44 , S 48 , and S 49 correspond to steps S 11 to S 15 in FIG. 4B .
- the heater 28 inherently shows long term degradation, that is, the heater 28 gradually increases/decreases the resistance thereof When such degradation occurs, for instance, the resistance of the heater 28 varies to R heater ′ from R heater , the heater power set by the initial heater current I heater — ini is given by:
- Step S 23 in FIG. 5A or step S 43 in FIG. 5B checks whether the heater power is within an acceptable range after the tunable LD 10 is practically activated.
- step S 24 or step S 44 carries out to correct the heater power, then the practical control to coincide the emission wavelength with the target wavelength. Even the heater shows the long term degradation, the control of the emission wavelength may be securely carried out.
- steps S 28 and S 29 in FIG. 5A or step S 48 and S 49 in FIG. 5B the sequence may add steps to check the heater power after the control of the emission wavelength.
- the sequence according to embodiments thus described configures with, what is called, the dual loop of the first loop L 1 for the tuning current and the second loop L 2 for the heater current.
- the heater 28 of the present invention is monolithically integrated in the tunable LD 10 , which the second loop L 2 shows relatively faster response even the loop L 2 controls the electrical power.
- the first loop L 1 for the tuning current is intentionally set in relatively greater time constant compared with that of the second loop L 2 to stabilize the dual loop control.
- FIG. 6 shows a functional block diagram of the dual loop control where the second loop L 2 for the heater current is accelerated.
- the second loop L 2 includes, in addition to the arrangement shown in FIG. 3 , an adder 60 and a functional unit 62 .
- the functional unit 62 performs the above arithmetic. This deviation of the heater current ⁇ I heater is added in the output of the second loop L 2 in feed forward, the response of the second loop L 2 may be accelerated.
- the embodiments describes that the SG-DFB region as the first region is stimulated to tune the emission wavelength by the injection current as the first stimulus.
- the SG-DFB region may provide a heater to tune the emission wavelength and the heater may be stimulated by the electric power supplied thereto.
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Abstract
Description
which deviates from the target heater power t_Pheater. Step S23 in
P+ΔP=(I heater +ΔI Heater)2 ×R.
Then, the deviation of the heater current ΔIheater becomes:
The
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CN112086857A (en) * | 2020-06-05 | 2020-12-15 | 哈尔滨工业大学 | Method and device for acquiring splicing position of continuously tunable laser and corresponding method and device for outputting continuously tunable laser |
US10985530B2 (en) | 2018-12-31 | 2021-04-20 | Electronics And Telecommunications Research Institute | Tunable semiconductor laser and operation method thereof |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
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CA2904819C (en) * | 2012-03-13 | 2018-10-02 | Danmarks Tekniske Universitet | Method of stabilizing a laser apparatus with wavelength converter |
JP6382506B2 (en) * | 2013-11-29 | 2018-08-29 | 住友電工デバイス・イノベーション株式会社 | Control method of wavelength tunable laser |
JP2015115411A (en) * | 2013-12-10 | 2015-06-22 | 日本電信電話株式会社 | High-speed wavelength sweep light source |
JP6422150B2 (en) * | 2014-07-03 | 2018-11-14 | 住友電気工業株式会社 | Wavelength tunable laser device and wavelength switching method |
US9312662B1 (en) | 2014-09-30 | 2016-04-12 | Lumentum Operations Llc | Tunable laser source |
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US9686018B2 (en) * | 2015-03-20 | 2017-06-20 | Sumitomo Electric Industries, Ltd. | Optical transmitter emitting light with narrowed linewidth |
US11764542B2 (en) * | 2017-12-15 | 2023-09-19 | Horiba, Ltd. | Semiconductor laser device, and method and program for driving the same |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003198054A (en) | 2001-12-28 | 2003-07-11 | Daitron Technology Co Ltd | Method and apparatus for driving wavelength-locked ld device |
JP2007201425A (en) | 2005-12-27 | 2007-08-09 | Eudyna Devices Inc | Laser device, laser module, semiconductor laser, and manufacturing method of same |
US20090021238A1 (en) * | 2007-07-19 | 2009-01-22 | Eudyna Devices Inc. | Optical device and method of controlling the same |
US20100272133A1 (en) * | 2009-04-27 | 2010-10-28 | Sumitomo Electric Industries, Ltd. | Wavelength tunable laser |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3334787B2 (en) * | 1996-05-22 | 2002-10-15 | 松下電器産業株式会社 | Oscillation wavelength stabilizing device for light source, harmonic output stabilizing device for light source, and optical disk system using them |
JP2003318481A (en) * | 2002-04-25 | 2003-11-07 | Sumitomo Electric Ind Ltd | Laser control circuit and laser module |
JP2005116549A (en) * | 2003-10-02 | 2005-04-28 | Sumitomo Electric Ind Ltd | Semiconductor laser drive circuit |
JP2009044024A (en) * | 2007-08-10 | 2009-02-26 | Eudyna Devices Inc | Semiconductor laser device, and control method of semiconductor laser |
JP4934557B2 (en) * | 2007-09-27 | 2012-05-16 | 株式会社日立製作所 | 4-level phase modulator |
JP5154581B2 (en) * | 2008-02-05 | 2013-02-27 | 住友電工デバイス・イノベーション株式会社 | Laser device and control data of laser device |
JP2010154123A (en) * | 2008-12-24 | 2010-07-08 | Toyota Motor Corp | Device including switched capacitor circuit |
-
2011
- 2011-10-18 JP JP2011228746A patent/JP2013089754A/en active Pending
-
2012
- 2012-10-17 US US13/653,958 patent/US8953650B2/en active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003198054A (en) | 2001-12-28 | 2003-07-11 | Daitron Technology Co Ltd | Method and apparatus for driving wavelength-locked ld device |
JP2007201425A (en) | 2005-12-27 | 2007-08-09 | Eudyna Devices Inc | Laser device, laser module, semiconductor laser, and manufacturing method of same |
US20090021238A1 (en) * | 2007-07-19 | 2009-01-22 | Eudyna Devices Inc. | Optical device and method of controlling the same |
US20100272133A1 (en) * | 2009-04-27 | 2010-10-28 | Sumitomo Electric Industries, Ltd. | Wavelength tunable laser |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10985530B2 (en) | 2018-12-31 | 2021-04-20 | Electronics And Telecommunications Research Institute | Tunable semiconductor laser and operation method thereof |
CN112086857A (en) * | 2020-06-05 | 2020-12-15 | 哈尔滨工业大学 | Method and device for acquiring splicing position of continuously tunable laser and corresponding method and device for outputting continuously tunable laser |
CN112086857B (en) * | 2020-06-05 | 2021-12-28 | 哈尔滨工业大学 | Method and device for acquiring splicing position of continuously tunable laser and corresponding method and device for outputting continuously tunable laser |
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